Infrared laser excites nonlinear crystals to generate 1064nm infrared light, and then frequency doubling to generate 532nm green light, which belongs to solid laser. Some green lasers operate in pulsed or quasi-continuous mode to reduce cooling problems and prolong battery life. The announced green laser that does not require frequency doubling has higher efficiency. Even low-power green light can be seen at night due to Rayleigh scattering from atmospheric molecules, and this high power laser pointer is often used by astronomers to point out stars and constellations. Green laser pointers can have various output powers. 5mW is the safest to use and is also visible in dim lighting, so no more power is needed for pointing purposes.
In today's society, the compact and easy-to-use green laser pointer has been widely used in conferences, teaching, museum visits, mountaineering, building inspections and other places as a light source for indication, and has a large market sales all over the world. The main structure of the green laser pointer is a miniature solid-state laser pumped by a laser diode (Laser Diode or LD).
Most commonly used laser pointer crystals
At present, the most commonly used crystal for making green laser pointer is a combination module of Nd:YV04+KTi0P04(KTP), in which NchYVO4 crystal generates 1064nm near-infrared laser, and KTP crystal converts 1064nm laser into 532nm green through intracavity frequency doubling For visible light output, the inner end faces of the two crystals are glued together, and the outer end faces are coated with a dielectric film that is conducive to pump light absorption, fundamental frequency laser oscillation, and frequency doubling output (such as Nd = YVO4 crystal outer end is coated with 808nm booster. Transparent and 1064nm, 532nm high-reflection film, KTP crystal outer end coated with 808nm, 1064nm high-reflection and 532nm anti-reflection film), thus forming a fundamental frequency light oscillation, green light output resonator, as shown in Figure 2.
Because NchYVO4 has the advantages of high absorption coefficient, large absorption cross section, large emission cross section, polarized emission, etc., combined with the advantages of large nonlinear coefficient and good beam quality of KTP, the light-to-light conversion efficiency of the green laser pen made from this is Higher, the output power is roughly 10mW~200mW. Although the use of Nd: YV04+KTP glued crystals is very common, this device still has the following shortcomings: (1) There are many determinants of device quality, including the quality of NchYVO4 crystals, the quality of KTP crystals, and the accuracy of the gluing process. etc. At the same time, the device process is more complicated, so the overall yield is low and the production cost is high. A low-power green laser pointer includes a battery, a circuit board, a switch, a pump source installed in a shell, and a crystal and an optical shaping system that are used as the laser working medium in sequence in front of the optical path of the output light of the pump source; It is characterized in that the crystal is a self-frequency-doubling crystal, and the self-frequency-doubling crystal is processed along the frequency-doubling phase matching direction. Frequency optical oscillation and 0.525-0.55μm frequency doubling output dielectric film, the thickness between the two light-passing end faces is 0.1-15mm; semiconductor laser diode pump light is injected into the self-frequency doubling crystal, after the pump light power reaches a certain value, The green laser is directly output by the self-frequency doubling crystal.